The realistic-looking weapon was found at the scene but it is understood that a closer examination has shown it to be an imitation.

It is believed the man, in his late 20s, has a psychiatric disorder and had not been taking his medication. The motorway was closed for eight hours, causing chaos for rush-hour travellers.

The shooting has been referred to the Police Complaints Authority and a detective chief superintendent from Cheshire has been appointed to head the inquiry.

Merseyside Police and GMP voluntarily referred the incident to the PCA. Nicola Williams, a PCA member who will supervise the investigation, said: "I am going to Greater Manchester to discuss the course of the inquiry with the senior investigating officer who will be Detective Chief Superintendent Kevin Hamilton from Cheshire Constabulary.

"A full report will be submitted to the Crown Prosecution Service and to the forces concerned."

The drama began in the man's home town of St Helens when Merseyside police were informed he was armed. Officers from Merseyside, Lancashire and Greater Manchester were chasing the suspect when he crashed his Ford Sierra near Shevington, Wigan.

The man stepped out of the car and waved what looked like a gun in the direction of police.

Negotiations started before one or more Merseyside officers opened fire, hitting the suspect in the leg. He was then taken to hospital, where his condition was described as "stable".